Voltage range as control input for OLTC-equipped distribution transformers

In many cases, the increasing load and the growing proportion of injected power from distributed energy generation results in the violation of voltage constraints in low voltage distribution grid. As an alternative to additional cables or substations, the application of distribution transformers equipped with on-load tap-changers (OLTC) is under development. This paper presents their benefits, and a method to control them with a voltage range as input parameter is proposed. The computational model for load flow calculation with OLTC, the simulation environment and the applied stochastic, synthetic profiles are described. The simulation results prove that the proposed method is suitable to keep the voltage within the constraints. It also features the advantage of less switching operations compared to a fixed voltage control method. This aspect leads to less wear and for this reason to a decrease of maintenance effort.